Rotary or rotational switches have been known and used for many decades and are known to include multiple connections points.
For example, a well-known type of rotary switch is a slide-type switch. Slide type switches include a conductive member that is rotated into various positions to close contact points where the conductive member contacts. In effect, these are mechanical contacts rotating against traces on, for example, a Printed Circuit Board (PCB). A major drawback of slide-type switches is that as the conductive member is slid, wear occurs due to the physical resistance of the conductive member against the rotational surface. This also has a tendency to cause wear to the contact points as well as the conductive member. In time, the connection between the conductive surface and the various contact points becomes attenuated and inconsistent. This leads to failure of the switch due to the lack of or the relatively poor electrical contact created.
Other types of rotary switches include Hall Effect sensors. These comprise a magnetic component(s) positioned as different angular locations about the rotatory switch, such that, when a magnetic component is rotated to a particular angular location, the device can read the magnetic component and interpret the angular position. These types of switches are non-contact type switches and therefore do not suffer from the wear problems associated with slide-type mechanical switches and therefore have very high reliability and life cycles. However, a major drawback of Hall Effect switches is that they are vulnerable to debris. Likewise, for a rotary switch that is able to determine multiple angular positions, a Hall Effect sensor is required for each angular position. This greatly increased the cost, the complexity and the size of the switch.
Still another type of rotary switch uses a Photo-interrupter sensors to determine angular position. These devices basically determine angular position by reading the outputs of various photo-interrupter sensors that are angularly displaced relative to each other such that, as the rotary switch is turned, the device can determine the position of the knob. These types of sensors, like the Hall Effect sensors, are a non-contact type of sensing device, which greatly increases the life cycle of the switch as they do not suffer from wear related issues. However, a major drawback of Photo-interrupter sensors is that, like Hall Effect sensors, they are vulnerable to debris. They are also very vulnerable to dust, which can obscure the light signals. Also, they too need to have Photo-interrupter sensors at each angular location that needs to be sensed, which increases the cost, complexity and size of the switch.
U.S. Pat. No. 6,236,002 (the '002 patent) outlines another approach has been to position protrusions on a cam that is rotatable and engages with various mechanical contacts that, upon rotation, will interact with the mechanical contact to cause it to form an electrical connection. Unfortunately, the structure of the '002 patent is rather complicated and requires a lot of space. For example, the mechanical contacts must be positioned radially offset from each other so as to be able to be actuated by the various protrusions at differing angular positions. Likewise, the mechanical contacts are subject to wear as they are physically moved based on the interaction of the protrusion with the mechanical contact. This physical interaction as the protrusion slides across the surface of the mechanical contact, will cause the mechanical contact to wear and fail.
U.S. Pat. No. 6,072,128 (the '128 patent) outlines still another approach where rotational movement of the rotary switch translates into linear movement of “contact bridges.” While the '128 patent does allow for reduced wear as it eliminates the sliding action of many prior art devices, the construction of the switch is large, complex and bulky. For example, the '128 patent comprises a body 3 that is inserted into a base 2 forming a device that has longitudinally extending channels. In these channels are linearly displaceable contact bridges and springs, which require longitudinal space. While the '128 patent may be useable in locations where space is prevalent, the longitudinally stacked components and complex construction make this switch configuration undesirable.
A need exists therefore, for a rotary switch that is simple in design, is small in depth, and does not suffer from the limitations and drawbacks outlined in connection with the prior art devices discussed above.